Many of the animals commonly seen in and around tide pools and along the beaches of Southern California are found in other parts of the world as well. What I share below are invertebrate animal species that I’m familiar with, as a lifelong California resident who has visited the beaches and explored the tide pools many hundreds of times.

Vertebrate species simply defined are animals that possess a backbone or spinal column, as in fishes, amphibians, reptiles, birds, and mammals. Invertebrate species then lack a backbone and spinal column, and include arthropods (such as insects, lobsters, and crabs), gastropods (such as snails and slugs), and others.[1]

The information shred below is about invertebrate species I’ve encountered in and around tide pools and tide pool areas here in Southern California. I published a separate article about vertebrate species.

What is listed here are what is most commonly seen, although many you may not see at all even after many visits and explorations. Some I’ve only rarely seen. For the most part, look and don’t touch. A few can be touched if you know what you’re doing, and I’ll explain which ones.

There are so many fun things to do at the beaches, although for me nothing tops tide pool exploration and searching for the animals that reside therein. Note that “tide pools” or “tidepools” are both correct – the word can be spelled either way.[2]

I’ve written many articles about animals, or the science of zoology, here on InfoBarrel and on my blog, and although I always try to write about any topic in a manner that anyone can understand, what is shared below is less technical than how I typically write. This is because this article intends to share information for travelers more than to be scientific.

They are technically a species of arthropod, like insects, lobsters, and crabs. However, they permanently attach themselves to rocks and sometimes other things such as boats, or even whales.[3]

Credit: Public domain.

Striped shore crab, very common along beaches and tide pool areas, and jetties in Southern California.[4]

Crabs

Non-hermit crabs can be a few inches across and typically walk and run sideways. They usually run away from people and hide amongst rocks. They’re often reddish in color.

I picked one up once and it pinched my finger and didn’t let go for about half an hour. They pinch surprisingly hard for how small they are.

The photo shown to the right is the most common type seen at Southern California beaches.[4]

Credit: Public domain.

Hermit crab.

Hermit crabs

Very amusing to observe, these crabs take the shells of dead sea snails and use them for a home. Then they have to find a bigger shell as they grow too large for the one they’re in.[5] The funniest thing is to see them fight over a shell, as they’re always looking for them.

Seeing one not in a shell is more rare, although I’ve seen it here and there.

Credit: Wikipedia photo by PretoriaTravel, CC BY-SA 3.0.

A beach explorer encounters a jellyfish on the beach, which appears as a shiny blob.

Jellyfishes

I mostly have seen them on the sand at the beach, and it should be known to avoid them because some species have a very painful sting. Some in the world are deadly, although they’re rare in Southern California.[6]

Oftentimes on the sand they might appear like a clear plastic bag. They have no skeleton and are often transparent, and their tentacles may be short or not visible. Be careful of anything like a transparent blob, as it could be a jellyfish.

My sister was stung by one while swimming in the ocean, and the sting took weeks to go away.

Credit: Wikipedia photo, CC BY-SA 2.5

California spiny lobster.

Lobsters

Classified as arthropods, as are insects, lobsters look somewhat like giant insects. They typically have long antennae, and can have strong claws. They often hide under rocks and are sometimes given away by antennae sticking out. One lobster species doesn’t have large front claws.[7]

In restaurants they keep them alive and throw them in boiling water to cook them, because when they die they secrete a highly toxic poison. So if it’s been dead for any length of time before being cooked, it’ll cause harm.[7]

Credit: Public domain.

Colony of mussels.

Mussels

A type of clam, this species often is found in large groups on rocks at the beach. They are edible for humans, and are also eaten by seagulls and starfishes.[8]

The shell is elongated and usually dark in color, often dark blue.[8] With some effort, they can be pried open and fed to seagulls, although in some places this may not be legal.

Credit: Wikipedia photo by albert kok, CC BY-SA 3.0.

Octopus.

Octopuses

My favorite tide pool animal. I only see them occasionally, and once I saw three in one day. They like to hide under rocks and only sometimes are seen swimming in the open, such as in a large tide pool. They change colors very quickly, and are the most amazing chameleons on Earth.[9]

They will spray a cloud of ink and turn bright red if they feel threatened. They are extremely intelligent, easily the most intelligent invertebrates.[9]

Octopuses are known for having eight tentacles. Squids are a close relative, and have ten tentacles.

Credit: Public domain.

Green sea anemone in California.

Sea anemones

Appearing somewhat like flowers, these animals with a bunch of small tentacles are closely related to jellyfishes.[10] You can gently touch their tentacles and observe the animal withdraw them quickly, although be aware that they’re very sticky. I wouldn’t recommend doing it unless you have someone show you how who has done it before.

Look at the spelling. Little kids often say it like “sea an-enemies.” The “m” and the “n” often get switched.

Credit: Public domain.

Sea hare in California.

Sea hares

This is a type of sea slug, and they often appear as a dark-colored blob, somewhat like a fat banana in size. You can lightly touch them, and they feel like the most slippery of anything on Earth. If you handle them too roughly though, they squirt toxic ink.[11]

Ensure you don’t step on any as you’re walking around. In some places they eat these animals, such as Hawaii and China.[11]

Credit: Public domain.

Sea urchins are animals and move very slowly.

Sea urchins

They have poisonous spines, and some people are allergic and can die – and it’s hard to know if you’re one of those people.[12] Be extremely careful not to step on one.

Some species are black or reddish and can be quite large. Most commonly you’ll see the smaller purple ones. These are animals and they move around, although slowly. They’re an invasive pest and cause a lot of problems for other species.[12]

Although it may not technically be legal in some places, I often pick up a rock and smash some of them up within a tide pool. Then I step back and wait, and other animals come out including fishes and eat them up.

Credit: Wikipedia photo by Tomasz Sienicki, CC BY 2.5.

Shrimp

Not always easy to tell apart from young lobsters, shrimp are closely related to lobsters. I’ve seen them in tide pools plenty of times, sometimes lots of them.[13]

The ones I’ve seen in Southern California are typically two to three inches in length, and pinkish or reddish in color.

In some countries they are known as prawns. Humans commonly eat the muscular tails.[13]

Credit: Public domain.

Bat star in California.

Starfishes

Shaped like stars, they can have five or more arms. They move around, although very slowly, and eat things with shells such as mussels. Some are orange, others are purple, and they come in a variety of colors and sizes. Some are very spiky. Some have long thin arms. They can grow their arms back if they get cut off.[14]

Starfishes and sea urchins are part of a group of animals called echinoderms, which only live in the oceans. Other well-known echinoderms include sand dollars and sea cucumbers.